The structural features and spatial relations in a digital terrain are definitive manner in terrain simulation by computer. It determines whether a digital terrain is similar to the natural ones. In the natural environment rivers are embedded in mountains. To bring this spatial modality into a stochastic terrain built by computer

a new method is introduced in this paper. In the method

a valley line is generated from a revised DLA model (Diffusion Limited Aggregation) controlled by sticking coefficient and mean field parameter. After a simplification of the valley line

a continuous expanding operation is used to establish the digital terrain subsequently. The experiment result shows that this method is controllable in the process of establishing the terrain. And the terrain is stochastic with natural dendritic valley in it.